This invention is directed to a lift beam assembly for attaching to and moving relatively heavy objects. It is more specifically directed to a redundant lift beam assembly incorporating mechanical latching mechanisms to outwardly extend and retract the lift arms from a relatively remote location.
In the past it has been common practice to utilize a pair or series of hook-like members which are suspended from each end of a laterally transverse beam. The beam usually has a ring attached near its mid-point so that the beam can be attached to and lifted by a crane hook. It was necessary, especially when lifting a heavy object, such as a vessel, cask or ladel, to move the beam and its associated hooks transversely across the object so that the beam and hooks can straddle and engage a pair of trunnions diametrically mounted on the sides of the vessel. Once the hooks were engaged, the beam could be raised so as to lift the vessel.
One of the major problems encountered with this type of arrangement is the necessity for a relatively large clear area along the side of the object to provide clearance for the movement of the crane to position the lift beam and hooks for engagement with the trunnions. Another problem was to prevent the hooks from disengaging. To resolve this problem, it was sometimes necessary for an operator to manually install a cross member to close the opening in the hooks to prevent their disengagement.
The hook arrangement had distinct limitations when it was necessary to provide redundant capabilities for safety purposes. This is especially true in the nuclear industry where safety is of paramount importance. Where it is necessary to lift a vessel or cask at four equally spaced points, the lift beam-hook arrangement is limited due to the fact that it is necessary to move the lifting assembly sequentially through two perpendicular directions to engage all of the conventional hooks.
The basic lifting assemblies used in the past have followed the design described above. When it was necessary to provide a specialty arrangement for hoisting heavy or bulky objects, various modifications have been suggested. One of these is described in U.S. Pat. No. 3,304,115 issued to W. B. Brooks et al. The lifting apparatus described in this patent is specifically designed for transferring a heavy load from an overhead crane to a front loading lift truck. This device provides a double beam assembly which is arranged in series to lift a heavy object such as a rocket motor. In use, an overhead crane engages the upper lift assembly which supports a lower or second lift assembly which is in turn attached by means of links to the object. When the lift truck engages the lower lifting assembly, the upward movement causes the ends of the links of the upper assembly to slide along the surfaces of a pair of outwardly sloped plates. This movement causes the upper links to spread so as to disengage the trunnions on the lower beam assembly.
In a similar way, U.S. Pat. No. 3,297,353, issued to Carlson, shows a truss assembly containing three scissor tongs spaced equally and arranged to engage the upper edge of a large concrete drainage pipe. After positioning the tongs over the edge of the pipe, upward force on the center of the assembly causes the tongs to close, gripping the pipe so that it may be raised and moved. This assembly shows the use of mechanical levers to perform the gripping operation and is typical of the lever approach for solving a lifting problem.
Another lifting assembly is disclosed in U.S. Pat. No. 3,287,057, issued to Gallapoo, which is used for lifting coils of sheet metal or the like. In this arrangement, the transverse beam has a pair of gripping jaws positioned at each end of the beam. The upward movement of the beam assembly causes the retraction of the jaws longitudinally with respect to the beam causing the jaws to grip the object along its sides. This gripping action is also reversed by the removal of the upward supporting force causing the jaws to extend and release their load.
None of these devices or any other known in the prior art provides a single fool-proof arrangement for engaging a heavy object when the object is surrounded and side clearance is restricted. This situation occurs quite often in the electrical or energy generating industry and especially in nuclear power plants. Because of the shielding requirements, heavy vessels for the reactors and casks containing radioactive materials are necessarily located in pits or water filled tanks which provide minimal side clearance around the vessel.
Another major problem especially prevalent in the nuclear industry is the manifest requirement for safety. The lifting and movement of objects, more especially heavy objects, presents problems which prior art devices can not effectively solve. Because of the catastrophic results that could occur upon the accidental failure of a lifting assembly and the dropping of a vessel, it is absolutely necessary that any lifting device which is directed to the side clearance engagement problem must also provide a high factor of safety during usage.
It is therefore an object of the present invention to provide a redundant lift beam assembly which can be used to engage and lift extremely heavy objects and to engage these objects even where there is limited side or lateral clearance.
It is a further object of the present invention to provide a redundant lift beam assembly which provides a substantial factor of safety to adequately and safely handle heavy objects containing hazardous or dangerous materials.
It is a still further object of the present invention to provide a lift beam assembly having a simple mechanical mechanism for outwardly extending and retracting lift arms in order to quickly and easily engage and release lifting trunnions.
It is a still further object of the present invention to provide a lifting assembly which is extremely foolproof in operation without the requirement for auxiliary equipment to provide a pressurized source of actuating power which is needed in all hydraulic or pneumatic systems.
It is a still further object of the present invention to provide a lift beam assembly which can be easily constructed and inexpensive to manufacture and yet has the strength capabilities to lift and move extremely heavy objects.
An additional object of the present invention is to provide a lift beam assembly in which the actuating latching mechanisms are capable of being operated by an individual from a remote location either above or below the lift assembly.